1. Field of the Invention
The present invention relates to a recording head for performing image recording in an image forming apparatus such as a copying machine, a facsimile apparatus, or a printer, and a method of mounting the recording head.
2. Related Background Art
Conventionally, a recording head of this sort includes an array of solid-state recording elements represented by LEDs (light-emitting devices) and driving circuits provided in a one-to-one correspondence with these recording elements. Accordingly, a driving IC formed by integrating these driving circuits is arranged parallel and adjacent to the solid-state recording element array, and the two chips are directly connected by a large number of bonding wires.
On the other hand, it is known that in the configuration of a recording head, the number of driving ICs and the number of bonding wires between the recording elements and the driving ICs can be extremely decreased when the emission efficiency of the recording elements is increased and the recording elements are time-divisionally driven. Furthermore, U.S. Pat. No. 5,451,977 has proposed the use of so-called self-scanning type recording elements, having a function of sequentially selectively scanning recording elements to be driven, in the chip of the recording element array.
Consequently, it is possible to separate a substrate on which recording elements are mounted and a substrate on which driving circuits for driving these recording elements are mounted and to miniaturize the recording head. Electrical connecting manner in this case are a method of directly connecting the recording elements and the bonding pads of the driving circuits by bonding wires and a method of connecting these parts by flexible cables.
As described above, the two methods can be used in electrically connecting the substrate on which the recording elements are mounted and the substrate on which the driving circuits for driving the recording elements are mounted. In the former method, the length of the wires is a few mm. Also, when the two substrates are connected at an angle of 90.degree., these two substrates are close to each other. Therefore, if the wiring density is high or the recording head is long, e.g., about 300 mm, the reliability of the electrical connection deteriorates.
On the other hand, the latter method increases the cost because the flexible cables are used. Additionally, a flexible connection region with a width of at least about 3 mm is necessary in the substrate on which the recording elements are mounted. Therefore, the recording head cannot be so miniaturized as in the former method.